Fold a sheet of aluminum foil in two and form a small "dish".  Pour enough lemon juice in foil to cover bottom and put fillets in.  Place a generous amount of butter on top of each fillet and sprinkle each with seasoned salt and parmesian cheese.  Add diced green peppers and onions and use another piece of foil to completely enclose fillets by folding over all edges.  Grill for 5 to 6 minutes on each side.  Drain juices and serve.